GB1573546A - Air nozzle assembly for use in apparatus for producing glass fibres - Google Patents

Description

PATENT SPECIFICATION ( 1) 1573546

Q ( 21) Application No 42850/77 ( 22) Filed 14 Oct 1977 ( 31) Convention Application No 52/026 935 ( 19) ( 32) Filed 11 March 1977 in ( 33) Japan (JP) etb ( 44) Complete Specification published 28 Aug 1980 ( 51) INT CL 3 CO 3 B 37/02 ( 52) Index at acceptance C 1 M 400 403 PL, ( 72) Inventors HIROAKI SHONO, SHINZO ISHIKAWA and ISAO \ WAKASA ( 54) AIR NOZZLE ASSEMBLY FOR USE IN APPARATUS FOR PRODUCING GLASS FIBERS ( 71) We, NITTO BOSEKI CO, LTD, a Corporation organised under the laws of Japan, of 1, Aza Higashi, Gonome, Fukushima-shi, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 5

The present invention relates to an air nozzle assembly for cooling a glass fiber drawing bushing by impinging air jet against the undersurface of an orifice plate used in an apparatus for forming glass fibers.

U.S Patent No 3,905,790 and U K Patent No 1,485,184 disclose a method and apparatus for forming glass fibers employing a generally flat orifice plate with orifices 10 which are closely spaced in flooding relationship, wherein a bulk flow of gas is directed upwardly to the orifice plate to cool molten glass cones formed at each orifice to provide a stable cone formation and to maintain separation of cones thus preventing flooding, to impinge on the orifice plate to eliminate stagnant gas adjacent to the plate, and to supply a source of gas sucked downwardly by the fibers 15 U.S Patent No 3,986,853 discloses an air nozzle effective to direct an air flow toward the orifice plate in the apparatus for forming glass fibers as described above As will be described in detail with reference to Fig 1, the air nozzle includes a plurality of air inlet pipes and a common discharge port so that the air forced through the air inlet pipes under a same pressure issue from the single discharge port as a bulk flow 20 In general, the cooling effect on the orifice plate is measured in terms of the force imparted by the air flow impinging against the orifice plate This force in turn is in proportion to the quantity and velocity of air flow That is, ( 1) F=K Q U where 25 F = force imparted to the orifice plate by the air flow; K= a coefficient; Q = a quantity of the air flow; and U = a velocity of the air flow.

If the quantity of an air flow is maintained constant, the air flows through a nozzle 30 having a smaller diameter at a faster speed than through a nozzle having a larger diameter That is, the air flow issuing from a nozzle having a smaller diameter exerts a greater force to an orifice plate than the air flow issuing from a nozzle having a larger diameter Furthermore the air flow or jet issuing from the nozzle diverges, and the pressure of the air flow decreases with the distance away from the axis of the nozzle As 35 a result the pressure of the air which impinges against the orifice also decreases with the distance away from the intersection between the axis of the nozzle and the orifice plate.

In general orifice plates are made of a metal having a high thermal conductivity such as platinum so that the orifice plate has a tendency to be quickly cooled by air to a uniform temperature within a predetermined area For instance when the distance be 40 tween the orifice plate and an air nozzle is 100 to 180 mm, which is the most preferable distance in practice, an area equal to 9 to 16 times the diameter of the air nozzle on the orifice plate may be uniformly cooled That is, the uniformly cooled area on the orifice plate is in proportion to the cross sectional area of the air nozzle so that the greater the diameter of the air nozzle, the greater the uniformly cooled area on the 45 orifice plate becomes The pressure P exerted from the air which impinges against the orifice plate is given by ( 2) P = F/A where A= area of the uniformly cooled area on the orifice plate Thus an air nozzle with a larger diameter will attain less cooling effect, but when the diameter of the air 5 nozzle is too small, the effectively, uniformly cooled area decreases so that the area of an array of orifices formed in the orifice plate is limited Therefore the air nozzle of the type disclosed in said U S Patent No 3,985,853 has the following problems:

( 1) Since a plurality of air flows supplied through a plurality of inlet pipes are joined together and a single air flow continuously issues from the single port, satis 10 factory cooling effect cannot be attained as with the case of an air nozzle having a larger diameter.

( 2) If the flow quantity of cooling air is increased in order to attain high cooling effect, turbulence is produced so that the orifices in the orifice plate cannot be cooled uniformly; that is, the temperature distribution in the orifice plate is not uniform In 15 addition the filaments drawn through the orifices in the orifice plate are bowed or deflected As a result filament breakage tends to occur very often Thus with the air nozzle of the type described, stable spinning of glass fibers cannot be ensured.

One of the objects of the present invention is therefore to provide an air nozzle assembly for use in a method and apparatus for forming glass fibers capable of giving 20 an excellent cooling effect with a minimum consumption of cooling air so that stable glass fibre spinning may be ensured.

According to the present invention, we provide an air nozzle assembly for cooling a glass fiber drawing bushing including an orifice plate having a flat undersurface and a plurality of closely-spaced orifices disposed in an elongated array, said nozzle assembly 25 comprising a support, a plurality of tubular nozzles mounted on said support so that their discharge ports are spaced apart from one another and arranged in a single row, means for supplying air to said nozzles and means for positioning said nozzles beneath said bushing so that said row extends in the longitudinal direction of said array but is offset from the longitudinal centerline of said array and said nozzles are aimed directly 30 at said undersurface of the orifice plate to discharge individual streams of air which directly impinge upon associated local areas of said undersurface.

The features and advantages of the present invention will become apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings, in which: 35 Fig 1 is a front view, partly in section, of a prior art air nozzle;

Figs 2 and 3 are front and side sectional views, respectively, of an apparatus for forming glass fibers incorporating an air nozzle assembly in accordance with the present invention; Figs 4 and 5 are front and rear views, respectively, used for the explanation of the 40 method for mounting tubular air nozzles on a support; Fig 6 is a top view of an air nozzle assembly according to the present invention having a plurality of tubular nozzles circular in cross section; and Fig 7 is a top view of an air nozzle assembly according to the present invention having a plurality of tubular nozzles elliptical in cross section 45 Prior to the description of the preferred embodiments of the present invention, the prior art air nozzle of the type disclosed in U S Patent No 3,986,853 will be described briefly with reference to Fig 1 in order to specifically point out the problems thereof which the present invention may overcome as will be described below Individual air flows at the same pressure are supplied through a plurality of air inlet pipes 50 1 arranged in parallel and are guided by guides 2 to diverge and then be diffused into a substantially single air flow, issuing from an opening 3 The air issuing from the opening 3 impinges against the whole undersurface of an orifice plate at a nearly uniform pressure so that the orifice plate may be uniformly cooled However, the air nozzle is in fact equivalent to a single nozzle having only one hole of a relatively larger diameter 55 so that the cooling capacity is low as described previously If the flow quantity is increased in order to increase the cooling capacity, turbulence is produced in the vicinity of the orifice plate so that uniform cooling cannot be attained Furthermore, the increased air jet blows away and deflects the glass filaments being drawn, consequently 60 causing filament breakage In Figs 2 and 3 there is shown an apparatus for producing glass fibers incorporating therein an air nozzle assembly in accordance with the present invention Molten 1,573,546 glass 4 which is supplied from a forehearth flows down through a bushing screen 5 into a bushing Electric current flows through terminals 6 so that the bushing may be maintained at a suitable temperature The molten glass in the bushing flows through a great number of orifices 8 of an orifice plate 7 into the atmosphere to form individual filaments 9 which are mechanically drawn downward Concurrently, air jets issuing from 5 an air nozzle assembly impinge against the undersurface of the orifice plate 7 so that the adjacent cones of molten glass formed on the undersurface of the orifice plate 7 may be prevented from coalescing with each other.

The air nozzle assembly N in accordance with the present invention includes a plurality of tubular nozzles 10 which are mounted on a support 11 in one row and 10 parallel with each other The support 11 in turn is held in optimum position by a positioning stand 12.

Figs 4 and 5 are the front and rear views, respectively, of the air nozzle assembly N in accordance with the present invention including a plurality of tubular nozzles 10 mounted on the support 11 The support 11 is formed with a plurality of insertion holes 15 13 having a diameter slightly greater than the outer diameter of the tubular nozzles 10, and the tubular nozzles 10 are inserted into and extended through these tubular nozzle receiving holes 13 and are securely held in position with setscrews 15 or the like screwed into tapped holes 14 drilled into the support 11 A raised portion centrally located on the rear surface of the support 11 between its ends is formed with a plurality of tapped 20 holes 16 which are used for mounting the air nozzle assembly N on the positioning stand 12 which permits the air nozzle assembly N to move up and down, back and forth and to right and left and to rotate so that the air nozzle assembly N may be held in optimum position relative to the orifice plate 7 The lower ends of the tubular nozzles 10 are connected to hoses 17 which in turn are communicated with an air source not 25 shown Air jets issuing from the tubular nozzles 10 flow upward to cool the filaments being drawn and the cones of molten glass at the undersurface of the orifice plate 7 and impinge against the undersurface of the orifice plate 7 to cool it.

In general the orifice plate 7 is rectangular in shape and is formed with more than 800 orifices so that the discharge ports of the tubular nozzles 10 are arranged in parallel 30 with one of the longer sides of the orifice plate 7 and are spaced apart from each other by a suitable distance As best shown in Fig 6, the tubular nozzles 10 are in general circular in cross section and are preferably made of a metal such as copper, aluminum, brass, steel or stainless steel, though not limited thereto The optimum cooling effect can be obtained when the cross sectional area of each of the tubular nozzles 10 is be 35 tween 40 and 100 mm 2 When the cross sectional area is too small, some local areas of the orifice plate 7 are cooled excessively with a resultant non-uniform temperature distribution in the orifice plate 7 On the other hand when the cross sectional area is too great, a satisfactory cooling effect cannot be attained, and the flow quantity of air must be increased in order to compensate for the unsatisfactory cooling effect However 40 when the flow quantity of the air jets is increased excessively, the filaments being drawn are blown away and deflected and the adjacent cones of molten glass on the undersurface of the orifice plate 7 are caused to join with each other so that filament breakage results It is preferable that the distance between the axes of the adjacent tubular nozzles 10 be as short as practicable, but the shorter the distance between the axes of 45 the adjacent tubular nozzles 10, the greater the number of tubular nozzles 10 mounted on the support 11 becomes and consequently the greater the flow quantity of air becomes.

The air nozzle assembly N with the above construction may attain various advantages as described below 50 ( 1) As compared with the prior art air nozzles, it may permit an operator in a shorter time and in a simpler manner to separate the individual glass filaments from the coalesced cones of molten glass formed on the undersurface of the orifice plate 7.

( 2) As compared with the prior art air nozzles, higher cooling efficiency may be attained with a smaller flow quantity of air 55 ( 3) The orifice plate may be uniformly cooled.

( 4) The bowing or deflection of glass filaments which results in filament breakage may be substantially eliminated.

( 5) The air nozzle assembly is simple in construction so that it may be fabricated in a simple manner at less cost 60 In addition, when the discharge end portions of the tubular nozzles 10 are extended from the support 11 so as to provide a space between each pair of adjacent tubular nozzles 10, as shown in the drawings, the air between the adjacent tubular nozzles 10 is entrained by the air jets issuing from the nozzles 10 and consequently the volume of the air impinging against the undersurface of the orifice plate 7 is greater 65 1,573,546 than the volume of air actually supplied through the hoses 17 In general, the smaller the diameter of the tubular nozzles 10, the more air is entrained by the air jets issuing from the nozzles 10.

Furthermore, as shown in Fig 3, the tubular nozzles 10 are inclined at an angle relative to the orifice plate 7 so that the width of the area of the orifice plate 7 against 5 which air jets impinge is increased As a result, the width of the area of the orifice plate 7 which is uniformly cooled is three to four times the diameter of the discharge port of the tubular nozzles 10 (it is almost equivalent to the area of 9 to 16 times the diameter of the discharge port), the area being also dependent upon certain other factors, notably the density of the tubular nozzles 10, the volume of air entrained by the air jets issuing 10 therefrom, and the thermal conductivity of the orifice plate Since the effective area of the undersurface of the orifice plate which is cooled by the air jets is greater than the total cross sectional area of the individual tubular nozzles 10 as described above, the distance between the centers of the adjacent tubular nozzles 10 which are arranged parallel with the longer sides of the orifice plate 7 may be increased and consequently 15 the tubular nozzles 10 may be decreased in number As a result, the volume of air supplied or the consumption of air may be decreased.

Next some examples of the present invention will be described.

Example 1.

For the sake of comparison the prior art nozzle of the type shown in Fig 1 and 20 with a discharge opening of the following dimensions was used.

length: 198 mm width: 7 mm cross sectional area: 1 386 mm 2 25 number of inlet pipes: 10 The dimensions of the air nozzle assembly in accordance with the present invention used in this Example are:

inner diameter: 8 4 mm cross sectional area: 55 mm 2 number of nozzles: 16 30 total cross sectional area: 887 mm 2 pitch: 12 mm These air nozzles were used in conjunction with an orifice plate with the following dimensional data:

width of an array of orifice holes: 32 4 mm 35 length of the array of orifice holes: 200 7 mm number of orifice holes: 2000 throughput: 800 grams/min.

1,573,546 1,573,546 The results are:

Prior Art The Invention

Separation time 35 min 8 min.

Temperature distribution on an orifice plate + 501 C + 30 C Flow quantity of air required for lowering the orifice plate by 100 WC 3 0 m'/min 1 5 m'/min.

Deflection of filaments yes negligible Example 2.

Three orifice plates A, B and C with the following dimensions were prepared:

A B C Number of orifice holes 800 2000 4000 Width of orifice hole array in mm 24 32 38 Length of orifice hole array in mm 73 200 340 Throughput gram/min 300 850 1500 6 1,573,546 6 Three air nozzle assemblies A', B' and C' were prepared according to the invention for respective orifice plates A, B and C.

A' Be C' Inner diameter of air nozzle in mm 7 9 11 Total cross sectional area in mm 2 269 1018 2376 Number of nozzles 7 16 25 Pitch in mm 9 11 5 1 l Flow quantity of air in liter/min 580 1750 3200 The air nozzle assemblies cooled the orifice plates satisfactorily and uniformly so that a continuous glass fiber drawing operation was possible 5 With tubular nozzles which are circular in cross section, the orifice plate may be satisfactorily cooled in the longitudinal direction thereof However the uniform cooling of the orifice plate in the lateral direction thereof may be attained only when the diameter of the tubular nozzles is greater than one quarter of the width of the orifice hole array in the orifice plate That is, when the diameter of nozzles is less than a 10 quarter of the width of the orifice hole array, the orifices outside of the areas against which impinge the air jets are not effectively cooled, so that the cones of molten glass at these orifices tend to coalesce to each other In order to overcome this problem, the present invention further provides air nozzle assemblies having tubular nozzles which are elliptical in cross section, as herein defined In this specification the term " ellipti is cal " refers to any cross section similar to an ellipse having a major axis and a minor axis and being symmetrical about these major and minor axes; more specifically, it includes not only an oval cross section and but also a cross section whose outline is defined by two parallel sides equal in length together with convex semicircular or elliptical curves connecting the ends of these sides The minor axes of the tubular nozzles 20 ' elliptical in cross section are arranged parallel with the longitudinal direction of the orifice plate as shown in Fig 7 Thus the orifice plate may be uniformly cooled in the lateral direction thereof.

The tubular nozzles elliptical in cross section may be fabricated by pressing tubular nozzles circular in cross section to flatten them or heating them over a die or directly 25 passing blanks through a die adapted to form a tubular nozzle elliptical in cross section.

Tubular nozzles rectangular in cross section may be also used in the present invention, but the fabrication thereof is rather expensive.

The tubular nozzles may be elliptical in cross section throughout their length.

Alternatively, they may be elliptical in cross section over a predetermined length from 30 their discharge ports with the remaining length being circular in cross section It is preferable that the distance between the centers of adjacent tubular nozzles elliptical in cross section be less than three times the length of the minor axis.

With tubular nozzles elliptical in cross section, the width of the array of orifices in the orifice plate may be increased to 60 mm from the width of 40 mm which is 35 typical of the prior art orifice plates cooled by the prior art air nozzles The number of orifices in one orifice plate therefore may be increased by 1 5 times as compared with the prior art Furthermore the width of the orifice plate may be increased while the length thereof may be decreased as compared with the prior art orifice plates so that

7 1,573,546 7 the volume or capacity of the spinning furnace may be decreased The width, or length in the lateral direction, of the region of the orifice plate which is cooled by the air jets issuing from these tubular nozzles elliptical in cross section is three to four times the length of the major axis Thus the width of the region that may be effectively cooled by the air jets, and correspondingly its area, may be considerably increased Furthermore 5 even though the tubular nozzle circular in cross section is flattened to have an elliptical cross section, the cross sectional area of the tubular nozzle elliptical in cross section is substantially equal to the cross sectional area of the tubular nozzle circular in cross section so that the air consumption remains almost the same Furthermore the velocity of the air jet is higher as compared with the prior art, so that the force exerted on the 10 orifice plate by the air jet is increased and consequently a more effective cooling effect may be attained The advantages of the tubular nozzles elliptical in cross section may be summarized as follows:

( 1) The orifices in the lateral direction of the orifice plate may be increased in number: 15 ( 2) The cooling area in the lateral direction on the orifice plate may be increased without increasing the cross sectional area of the tubular nozzles elliptical in cross section and thus without decreasing the velocity of air jets That is, the air jets impart higher forces to the orifice plate with a small volume of air so that high cooling efficiency may be attained 20 ( 3) The filaments are not subjected to bowing or deflection.

Next some examples of air nozzle assemblies having tubular nozzles which are elliptical in cross section will be described.

Example 3.

An orifice plate having the folowing dimensions was prepared 25 number of orifice holes: 4050 width of array of orifice holes: 46 0 mm length of array of orifice holes: 344 0 mm throughput: 1600 gram/min.

When an air nozzle assembly having a plurality of tubular nozzles circular in cross 30 section was used, the cooling of the orifice plate was unsatisfactory especially in the vicinity of the longitudinal edges thereof To overcome this problem an air nozzle assembly having tubular nozzles elliptical in cross section with the following dimensions was prepared:

cross section: ellipse 35 major axis: 13 mm minor axis: 5 mm number of nozzles: 30 pitch: 11 mm total air flow rate: 3 2 ms/min 40 Stable glass fiber spinning was possible.

Example 4.

An air nozzle assembly with the following dimensions was prepared:

cross section: circular inner diameter: 8 5 mm 45 number of nozzles: 20 total flow rate: 1 7 m'/min.

With this air nozzle assembly, the largest orifice plate which could be satisfactorily cooled was as follows:

number of orifice holes: 2008 50 width of array of orifice holes: 32 0 mm length of array of orifice holes: 2520 mm throughput: 850 gram/min.

An air nozzle assembly with the following dimensions was also prepared:

cross section of nozzles: elliptical major axis: 11 0 mm minor axis: 5 5 mm number of nozzles: 20 5 total flow rate: 1 7 min/min.

With this air nozzle assembly, the largest orifice plate which could be satisfactorily cooled had the following dimensions:

number of orifice holes: 2008 width of array of holes: 38 0 mm 10 length of array of holes: 207 9 mm drawing speed: 850 gram/min.

As a result it was possible to reduce the length of the bushing by about 20 mm.

Claims (9)

WHAT WE CLAIM IS:-

1 An air nozzle assembly for cooling a glass fiber drawing bushing including an 15 orifice plate having a flat undersurface and a plurality of closelyspaced orifices disposed in an elongated array, said nozzle assembly comprising a support, a plurality of tubular nozzles mounted on said support so that their discharge ports are spaced apart from one another and arranged in a single row, means for supplying air to said nozzles and means for positioning said nozzles beneath said bushing so that said row extends 20 in the longitudinal direction of said array but is offset from the longitudinal centerline of said array and said nozzles are aimed directly at said undersurface of the orifice plate to discharge individual streams of air which directly impinge upon associated local areas of said undersurface.

2 An air nozzle assembly as set forth in Claim 1 wherein said plurality of tubular 25 nozzles are mounted on a support in such a way that their leading portions may be extended beyond said support.

3 An air nozzle assembly as set forth in Claim 1 wherein the cross sectional configuration of each of the discharge ports of said plurality of tubular nozzles is circular.

4 An air nozzle assembly as set forth in Claim 3 wherein the diameter of the dis 30 charge ports of said plurality of tubular nozzles is greater than a quarter of the width of an array of orifice holes formed in said orifice plate.

An air nozzle assembly as set forth in Claim 4 wherein the cross sectional area of said discharge port is 40 to 100 mm 2.

6 An air nozzle assembly as set forth in Claim 1 wherein the cross sectional con 35 figuration of each of the discharge ports of said plurality of tubular nozzles is elliptical, as herein defined, with the minor axes thereof being arranged in line and in parallel with the longitudinal direction of an array of orifice holes formed in said orifice plate.

7 An air nozzle assembly as set forth in Claim 6 wherein the major axis of said discharge ports is greater than a quarter of the width of an array of orifice holes formed 40 in said orifice plate.

8 An air nozzle assembly as set forth in Claim 6 wherein the distance between the centers of the adjacent discharge ports is less than three times the minor axis thereof.

9 An air nozzle assembly according to claim 1 and substantially as described herein with reference to Figures 2-7 of the accompanying drawings 45 For the Applicants, CARPMAELS & RANSFORD, Chartered Patent Agents, 43 Bloomsbury Square, London WC 1 A 2 RA.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980.

Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A 1 AY, from which copies may be obtained.

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